Field of the Invention
The present invention is directed to materials for filling dental root canals, and in particular dental root canal filling cones or points, and process of sterilizing such cones/points.
Description of Related Art
Dental root canal treatment generally involves three stages: shaping, cleaning and obturation (generally involving filling and sealing). The purpose of performing dental root canal treatment is to remove infected dental pulp tissue inside the pulp chamber and root canals, and to fill/seal the vacant space with a biocompatible material. More specifically, the ultimate objective of root canal treatment is to eliminate the infection inside the dental root system and to tightly seal or obturate, in three dimensions (3-D), the tiny openings at the end of the root canal, (referred in the profession as an apex).
Heretofore, root canal treatment processes involve placement of a root canal filling and/or sealing point or cone in a prepared root canal to plug the root canal, ideally in a manner to eliminate micro-leakage. Hereinafter, the term “point” and “cone” will be used interchangeably to refer to dental root canal filler/sealer.
The most commonly used root canal filling material for many years is a biocompatible latex compound commonly called Gutta Percha (GP), which comprises polyisoprene, or trans-polyisoprene with a chemical composition of 1,4-trans-polyisoprene (TPI). Other thermoplastic polyurethane based compounds may be adopted. The filling material is made into cone/point shape with different diameter sizes at the tip of the cone. When heated, the material will soften to flow at rather low temperature settings, typically starting at 60 to 80 degree Celsius. In this soften state, users (dentists or specialists known as endodontists) can mold/pack filling material all the way into root canal system for optimum obturation, filling and sealing effects. The filling material is chemically inert, and is therefore more biocompatible. Gutta Percha also hold its dimension quite well when change from heated liquid alpha phase to cooled solid beta stage.
Typically, the filling cones are supplied in bulk (with 50 to 100 cones within a plastic container) and are non-sterile. It has been long desired by endodontists (e.g., by pioneer endodontist Dr. Louis I. Grossman's standard) that these filling cones should be sterilized prior to insertion into root canals of in vivo teeth. Failure to completely sterilize the root canal sealing cone could lead to future bacteria colonization inside the root canal system, and re-infection and possible loss of the tooth. Due to the low melting temperature threshold for GP material, the most widely used and very effective heat based sterilization method such as heat steam autoclave is however off limits. Heretofore, throughout the years, clinicians and researchers have tried so-called “cold sterile” technique with different chemical agents, such as Sodium Hypochlorite, Glutaraldehyde, and Chlorhexidine. Research papers have shown that these agents require sufficient time to be adequate to achieve sterilizing effect, sometimes hours for these chemical agents to take effect. This raises two fundamental questions: (a) are these chemical agents bactericidal or bacteriostatic; and (b) are the results achieved by using these chemical agents simply disinfection or true sterilization. (Generally, disinfection and sterilization are both decontamination processes. Disinfection generally refers to the process of eliminating or reducing harmful microorganisms from inanimate objects and surfaces; sterilization generally refers to the process of killing substantially all microorganisms; these being the main difference between sterilization and disinfection.)
Furthermore, there also are additional issues concerning use of these chemical agents in daily clinical setting. (1) Chemical sterilization/disinfection has to be carried out in a treatment room, by the patient's chairside, just prior to use. The vapors of these chemical agents produce strong odors, and are considered harmful to the patient. (2) The root canal filling cones are generally supplied in bulk (e.g., 50 to 100 units in each pack) and in a non-sterile condition. Since the sterilization/disinfection process can take a long time, it raises a serious question whether dental clinicians and nurses are complying with sterile protocol in their busy practice. (3) Cold chemical sterilization process is traditionally considered as surface sterilizer. When a “cold sterilized” root canal filling cone had been inserted into a root canal, heated and melted for three-dimensional molding condensation and tight seal, the inside non-sterile core material of the filling cone will become exposed to the outside. As a result, the filling material becomes contaminated and non-sterile.
Still further, there is a problem that the material for root canal that includes mainly Gutta Percha is easily deteriorated due to sterilization.
There remains an unresolved need to provide Gutta Percha based root canal filling points/cones that are sterilized prior to shipment to the endodontists.